Enable linear EE Group ancestors queries

In this commit, we're removing the feature flag
`linear_ee_group_ancestor_scopes` to allow
EE Group using linear queries.

Changelog: added
EE: true

config/feature_flags/development/linear_ee_group_ancestor_scopes.yml

----
-name: linear_ee_group_ancestor_scopes
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/70708
-rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/341350
-milestone: '14.4'
-type: development
-group: group::access
-default_enabled: false

ee/app/models/ee/group.rb

@@ -624,13 +624,7 @@ module EE
     end
 
     def invited_or_shared_group_members(groups)
-      groups_and_ancestors = if ::Feature.enabled?(:linear_ee_group_ancestor_scopes, self, default_enabled: :yaml)
-                               groups.self_and_ancestors
-                             else
-                               ::Gitlab::ObjectHierarchy.new(groups).base_and_ancestors
-                             end
-
-      ::GroupMember.active_without_invites_and_requests.where(source_id: groups_and_ancestors)
+      ::GroupMember.active_without_invites_and_requests.where(source_id: groups.self_and_ancestors)
     end
 
     override :_safe_read_repository_read_only_column

ee/spec/models/ee/namespace_spec.rb

@@ -1165,14 +1165,6 @@ RSpec.describe Namespace do
       end
 
       it_behaves_like 'billable group plan retrieval'
-
-      context 'when feature flag :linear_ee_group_ancestor_scopes is disabled' do
-        before do
-          stub_feature_flags(linear_ee_group_ancestor_scopes: false)
-        end
-
-        it_behaves_like 'billable group plan retrieval'
-      end
     end
   end